面向对象三大特性----多态

多态使用前提：1.对父类进行重写或对接口进行实现 2.向上转型。

abstract class People {

    abstract void sleep();

    abstract void eat();
}

class Student extends People {
    void sleep() {
        System.out.println("我睡了");
    }

    void eat() {
        System.out.println("我吃了");
    }

}

class Student2 extends People {
    void sleep() {
        System.out.println("我不睡");
    }

    void eat() {
        System.out.println("我不吃");
    }

}

class PeopleRun {
    public static void run(People p) {
        p.sleep();
        p.eat();
    }
}

public class Demo {
    public static void main(String[] args) {
        PeopleRun.run(new Student());
        PeopleRun.run(new Student2());
    }
}